The name of the third day of the week in Sindarin was dedicated to Ithil, the Moon. Its equivalent in Quenya was Isilya, with the same meaning. The idea of a day named for the Moon passed to Númenor, where the Elvish day-name was preserved, and on to Middle-earth, where it was rendered into the Common Tongue. There, it became Monendei, and later simply 'Monday'.